Parallax barrier protecting means for cathode ray tubes having patterned screens



March 17, 1970 G. A. BURDICK 3,501,663

PARALLAX BARRIER PROTECTING MEANS FOR CATHODE RAY TUBES HAVING PATTERNEDSCREENS Filed Aug. 12, 1968 INVENTOR. GLEN A. BURDIGM ATTORNEY UnitedStates Patent US. Cl. 313-85 4 Claims AESTRACT OF THE DISCLOSURESupport-springs for color cathode ray tube parallax barriers have anoutwardly projecting portion formed thereon to extend from the aperturedfree end of the spring to prevent damaging contact of the barrier withan inwardly extending supporting stud formed on the interior wall of thecathode ray tube face plate during the insertion of the barrier withinthe face plate.

Background of the invention This invention relates to cathode ray tubeshaving a patterned cathodoluminescent screen with a parallax barrierpositioned between the screen and a source of electrons and moreparticularly to a color cathode ray tube of the shadow mask varietywherein the mask is releasably mounted within the face plate of the tubeby means of leaf springs having one end connected in supportive relationto the mask and an apertured free end formed to engage an inwardlyextending stud formed on a wall of the face plate. Still moreparticularly the invention relates to means associated with the supportsprings for protecting the mask from damaging contact with the studsduring insertion thereof into the face plate. Color cathode ray tubes ofthe type in use today have patterned cathodoluminescent screenscomprised of discrete areas of phosphors that emit different coloredlight upon excitation by a cathode ray. The particular phosphor orphosphors selected for excitation is controlled by a particular electronbeam or beams and the parallax barrier as is well known in the art.

The patterned screens for this type color tube are prepared by aphotographic deposition technique wherein, by one of several knownmethods, a layer of phosphor and a photosensitized material is appliedto the screen area which is then exposed, by a point source of lightpassing through a patterned negative, to cause the exposed areas tobecome fixed in relation to the unexposed areas. The negative is thenremoved and the screen developed to form part of the final pattern. Theprocess is repeated for each of the different color light emittinphosphors desired in the finished tube.

In tubes of the shadow mask variety, the parallax barrier (or shadowmask) is composed of a fragile foraminous metal sheet having a thicknessof the order of .006 inch. This shadow mask is formed to besubstantially parallel to the screen surface (generally spherical inmodern tubes) and is fixed at its periphery to a frame havingsubstantially rigidity relative to the mask. The frame may be composedof a metallic material having a thickness of the order of .050 inch.This shadow maskframe assembly is supported within the face plate oftube and in spaced relation to the screen by means of leaf springsattached at one end to the frame and having apertured free endsextending therefrom. The apertured free ends are formed to cooperate insupporting relationship with inwardly projecting studs formed oninterior walls of the tube face plate. It is necessary that the mask bereleasably mounted in the face plate because it is utilized as thenegative in the screen formation process. Thus, during the formation ofthe screen the mask must be inserted and removed a minimum of threetimes. It 15 during insertion that damage to the mask is most likely tooccur. If an operator inserting the mask is careless or if the mask isnot properly centered in the face plate, damaging contact of the maskwith one or more of the mwardly projecting studs may occur. Because ofthe fragile nature of the mask such contact need only be slight to causea dent in the mask. Such a dent formed m the maskwhich, it is to beremembered, is used as the negative in the screen formation process-willcause an imperfect screen to be formed and result in the rejection ofthe finished tube.

Objects and summary of the invention It is an object of this inventionto enhance the fabrication of color cathode ray tubes.

It is another object of this invention to reduce the scrap or shrinkagein color cathode ray tube production and thus reduce the cost.

It is yet another object of the invention to improve the screen qualityof color cathode ray tubes.

Yet another object of the invention is to increase the facility withwhich an unskilled operator may insert parallax barriers in the faceplates of color cathode ray tubes without causing damage thereto.

These and other objects are accomplished in one aspect of the inventionby the provision on at least two of the support springs of means forprotecting the parallax barrier from damaging contact with the inwardlyprojecting studs during its insertion into the face plate.

Brief description of the drawings FIG. 1 is a sectional view of a colorcathode ray tube employing the invention;

FIG. 2 is a perspective view of one type of support spring utilizing theinvention; and

FIG. 3 is an alternate embodiment of the invention.

Description of the preferred embodiments For a better understanding ofthe present invention, together with other and further objects,advantages, and capabilities thereof, reference is made to the followingdisclosure and appended claims in connection with the above-describeddrawings.

Referring now to the drawings with greater particularity, in FIG. 1there is shown a typical color cathode ray tube 10 of the shadow maskvariety which comprises an envelope formed from a substantiallyfunnel-shaped body 12, an elongated neck 14 closing the small end of thefunnel, and a face plate 16 having an upstanding peripheral wall 17therearound closing the large end of the funnel. A patternedcathodoluminescent screen 18 is formed on the inside surface of faceplate 16 and a source of electrons in the form of one or more electronguns 20 is positioned in neck 14. Positioned intermediate guns 20 andscreen 18, but closer to screen 18, is a parallax barrier 22. In thisinstance parallax barrier 22 is shown as a shadow mask; and willhereafter be referred to as such; however, it is to be understood thatother types of bar riers may be utilized, such, for example, asswitching grids, aperture grills, focus masks, etc. The shadow mask 22is a thin, fragile, foraminous member having a thickness of the oder of.006 inch. A small upstanding wall 24 projects from the periphery of themask and is attached to a relatively rigid supporting frame 26. Theframe 26 is in turn mounted within the face plate 16 by means of aplurality of support springs 28 which are mounted in a supportingrelation at one end thereof to a wall frame 26 and at their free end toinwardly projecting studs 30 formed in spaced relation around wall 17 offace plate 16. Studs 30 are substantially frustoconical in configurationand mate conjnnctively with appropriately formed apertures 32 in thefree end 34 of springs 28.

Spring 28 is shown detail *in FIG. 2 as comprising a first portion 36and a second portion 34, previously men tioned as the free end, whichare substantially parallel.

The first and second portions are interconnected by an intermediatesection 38. Means 40 for protecting mask 22 from damage during,insertion into face plate 16 comprises a projecting portion 42 extendingfrom; the apertured end 34 of spring 28 toward mask 22. The distal end44 may be formed to project inwardly toward the center of the tube. Thusit will be seen that during insertion of the mask-frame assembly intoface plate 16, if the mask is off-center, it is the distal portionAZ ofmask protecting means 40 which will contact the inwardly projecting stud30. Obviously, mask protecting means 40 must not project toward mask 22a;distance great enough to interiere with.;the screen forming process.

In FIG. 3 is shown an alternate embodiment of the spring 28 wherein themask protecting means 40 has formed therein stud lead-in means 44 whichmay; be in the form of a groove extending from substantially theaperture 32 to the terminus of distal end 42. Additionally, when spring28 is so provided, the groove may have a widened entrance area 46 tofacilitate the entrance of stud 30 thereinto.

Thus, by this invention, the fabrication of color cathode ray tubes hasbeen greatly enhanced. Means have been provided which reduce shrinkagein tube manufacture and subsequent cost thereof. Further, the facilitywith which an unskilled operator may insert parallax barriers within theface plates of tubes, without damage thereto, has been increased.

While there have been shown and described what are at present consideredthe preferred embodiments of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be made 4therein without departing from the scope of the invention as defined bythe appended claims.

I claim:

1. In a cathode ray tube having a parallax barrier releasably mountedtherein between a patterned 'cathodoluminescent screen and a source ofelectrons, means for mounting said barrier in said tube comprising atleast two inwardly projecting studs formed around a wall of the tube anda like number of support springs formed to support said barrier andbeing further formed to provide at the free end thereof an aperture toreceive said inwardly projecting studs, the improvement comprising:

means integral with said at least two of said support springs forprotecting said parallax. barrier from damaging contact withzsaidinwardly projecting studs during its insertion into said tube.

2. The invention of claim 1 wherein said means for preventing damagingmask contact with said studs comprises a projecting portion extendingfrom the apertured free end of said spring toward said barrier andhaving. its distal end formed to project inwardly toward the center ofsaid tube. I

3. The invention of claim 2 wherein said distal end is spaced from saidbarrier.

4. The invention of claim 1 wherein said barrier is aflixed atsubstantially its periphery to a supporting frame having upstandingwalls and said support springs are affixed to said walls and said freeend is spaced there from.

References Cited UNITED STATES PATENTS 12/1955 Mark et al 313 8/1958Shrader 3l385

